1. Field of the Invention
The invention relates to a polyaxial bone anchoring device, in particular for use in spinal or trauma surgery. The polyaxial bone anchoring device comprises a bone anchoring element with a shank to be anchored in the bone and a head. The head is pivotably held in a receiving part and can be fixed at an angle by applying pressure onto it via a pressure element. The polyaxial bone anchoring device further includes a locking assembly comprising a first locking member being configured to exert pressure onto the pressure member and a second locking member provided in a bore of the first locking member, the second locking member being configured to exert pressure onto the rod. In a first configuration, the first and the second locking members are rotationally fixed relative to each other such that by rotating the second locking member in a first direction, the first locking member is advanced to contact the pressure member. In a second configuration, the second locking member is rotatable within the first locking member such that by rotating the second locking member in the first direction, the second locking member is advanced to contact the rod. With the locking assembly, the head and the rod can be fixed in a sequential manner using a tool with a single drive portion that engages the second locking member.
2. Description of the Related Art
US 2003/0100896 A1 describes a bone anchoring device with a shank and a receiving part connected to it for connecting to a rod. The receiving part has a recess having a U-shaped cross-section for receiving the rod with two open legs and an internal thread on the open legs. A locking assembly is provided comprising a nut member with an external thread that cooperates with the internal thread of the legs and a set screw. The nut member has on one end slits for engagement with the screw tool. The shank has a spherically-shaped head that is pivotably held in the receiving part. A pressure element is provided that exerts pressure onto the head when the nut member is tightened. By tightening the set screw the rod is fixed in a receiving part. Hence, the rod and the head can be locked independently from each other.
U.S. Pat. No. 7,972,364 describes a locking assembly for securing a rod in a rod receiving part of a bone anchoring device that includes a first locking element and a second locking element. With the first locking element and the second locking element the head of the bone anchoring element and the rod can be locked independently using a tool with two drive portions.
U.S. Pat. No. 8,088,152 B2 describes an orthopedic retaining system comprising at least one bone screw which has a head part and a threaded shaft pivotably mounted thereon. A clamping element is mounted in the head part, which can be pressed against the threaded shaft from its upper side and, as a result, secure the threaded shaft relative to the head part. A retaining bar is arranged in a receptacle of the head part. Further, a clamping device is provided on the upper side of the head part, by means of which the clamping element and the retaining bar are pressed into the head part such that the threaded shaft and the retaining bar are secured in positions relative to the head part. The clamping device comprises an elastically deformable pressure element which is displaced into a clamping position during actuation of the clamping device. With such a configuration, upon actuation of the clamping device, the pressure element abuts first on the clamping element and thereby secures the pivotable threaded shaft in position on the head part while the retaining bar remains freely displaceable. Only upon further actuation of the clamping device the pressure element is elastically deformed thereby abutting on the retaining bar and securing the retaining bar in position.